Fred Wilson wrote a good piece on this last year: http://avc.com/2014/03/the-bubble-question/
What is troubling, though, is the amount of personal data and privacy violations and voluntary surveillance we've trained the populace into accepting as collateral damage when trying to raise our valuations up and fix broken revenue models. That's, I fear, going to be what remains long after our fortunes have dwindled.
It's as though ad-supported companies are advertising each other to keep the money flowing because they can't get any outside money.